Nephrology consultation and mortality in people with stage 4 chronic kidney disease: a population-based study

BACKGROUND: Guidelines recommend nephrology referral for people with advanced non-dialysis-dependent chronic kidney disease, based mostly on survival benefits seen in retrospective studies of dialysis patients, which may not be generalizable to the broader population with chronic kidney disease. We aimed to examine the association between outpatient nephrology consultation and survival in adults with stage 4 chronic kidney disease. METHODS: We linked population-based laboratory and administrative data from 2002 to 2014 in Alberta, Canada, on adults with stage 4 chronic kidney disease (sustained estimated glomerular filtration rate >= 15 to < 30 mL/min/1.73 m(2) for > 90 d), who had never had kidney failure and had had no outpatient nephrology encounter in the 2 years preceding study entry. Participants who had never had an outpatient nephrology visit before renal replacement treatment were considered "unexposed." Participants who saw a nephrologist during follow-up were considered "unexposed" before the first outpatient nephrology visit and "exposed" thereafter. The primary outcome was all-cause mortality. RESULTS: Of the 14 382 study participants (median follow-up 2.7 yr), 64% were aged >= 80 years, 35% saw a nephrologist and 66% died during follow-up. Nephrology consultation was associated with lower mortality (hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.82-0.93). The association was strongest in people < 70 years (HR 0.78, 95% CI, 0.65-0.92), progressively weaker with increasing age, and absent in people >= 90 years (HR 1.05, 95% CI 0.88-1.25). INTERPRETATION: The survival benefit of nephrology consultation in adults with stage 4 chronic kidney disease may be smaller than expected and appears to attenuate with increasing age. These findings should inform recommendations for nephrology referral considering the advanced age of the patient population meeting current referral criteria.